Due to their small size, density, and fragile structure, miniature electronic components (such as ceramic capacitors and resistors) require special devices systems, and methods for their transportation, handling and processing. These components are generally square or rectangular in shape and are typically loaded into a part-handling plate, or carrier plate, for handling and processing as a batch. Conventional carrier plates are described in U.S. Pat. Nos. 4,526,129; 4,381,321; 4,395,184; and 4,393,808. These plates are typically rectangular and have an array of apertures for resiliently holding miniature components. These apertures often have a circular or elliptical cross section which is lined with a pliable elastic material such as silicon rubber or a resilient polymeric material. The apertures through the pliable material have slightly smaller dimensions than the electronic components such that the material grips the components continuously as they are loaded into the aperture. The depth of each resilient aperture is typically greater than the maximum length of the part to be inserted. Once inserted, the component is held in place inside the carrier plate aperture by the resilient material, thus allowing for further transport, storage, or processing. Generally each carrier plate has an array of uniformly sized holding apertures.
Conventional component insertion techniques are described in U.S. Pat. Nos. 4,669,410, 4,395,184, 4,393,808, 4,381,321, and 4,526,129. According to these patents, vacuum suction is used in conjunction with mechanical vibration to load components into an array of funnel shaped guide openings in a loading plate. The loading plate openings abut and are aligned with the pliable apertures of the carrier plate. Loading or holding plates of various configurations are described for example in U.S. Pat. Nos. 4,903,393 and 4,847,991. A bank of pins rigidly held in a mechanical press are used to push the components through the loading plate guide openings and into the aperture of the carrier plate. Once the components have been pushed into the carrier plate apertures, the press pins are extracted, leaving the components held in place by the elastic material of the carrier plate. Termination press pins and their mounting plates are described in U.S. Pat. Nos. 4,381,321, 4,903,393, and 4,395,184. Miniature electronic components are typically processed in large scale batch fashion. Any factors which slow down or halt operation will greatly reduce the component throughput of the entire process.
Problems occur with conventional press pin configurations when excessive resistance is encountered in inserting the components. Such resistance can result from incorrect matching of the pin array with the array of openings in the loading or carrier plates, from debris or additional components in the insertion aperture, or from incorrect positioning of the components. Similar problems occur when a single press plate is used to insert workpieces of varying sizes into a holder having a positive stop. When the larger workpieces reach the positive stop, they can be subject to crushing force as the press plate continues to push the smaller components to the positive stop.
Any of these phenomena may result in damage to the press pins, the load plate, the carrier plate, or the component itself. Also, if a damaged press pin goes undetected during processing, it becomes a source of further damage to other components or equipment. Because the typical press contains a large number of pins (often thousands of pins per plate) the potential for pin damage is great. Replacing damaged pins requires substantial processing downtime. To reduce this downtime, manufacturers maintain large inventories of spare press equipment, adding to processing costs.
The problems mentioned above could be solved in part by using pressure sensors to detect excess loading resistance to the action of the entire press plate. With this approach, however, the loading cycle for all positions would have to be halted to prevent damage to an obstructed pin. It would be highly desireable to have a means of detecting and preventing pin damage which would not require halting the entire pressing cycle. In addition, a method of simply and quickly detecting the location of obstructed aperture is also desirable. Such a system would increase processing throughput, reduce operating costs, extend the useful life of the equipment assemblies and facilitate the identification and repair of damaged pins in a press plate.
A first object of the present invention is to provide a method of protecting press pins from damage caused by excessive loading resistance. A second object of the present invention is to provide a method of protecting press pins such that the pressing operation need not halt for all positions. A third object of the present invention is to provide a method of easily detecting obstructed or improperly aligned component loading apertures. Other and further objects of the invention will be apparent in light of the following disclosures.